1. Field of the Invention
The present invention relates to a plasma display panel, and more particularly, to a structure for joining substrates of a plasma display panel.
2. Description of the Related Art
Flat panel displays are used for wall-mounted televisions, computer screens, and other such display applications. Among the different types of flat panel displays, the plasma display panel (PDP) is emerging as one of the most promising flat panel display configurations. Predetermined images are realized by the PDP by a discharge mechanism occurring in discharge cells.
As with other flat panel displays, such as, vacuum fluorescent displays and field emission displays, PDPs include two substrates (hereinafter referred to as an upper substrate and a lower substrate) which are provided substantially in parallel with each other and with a predetermined gap therebetween. The substrates define an exterior of the display device. A sealant is provided around an outer circumference of opposing surfaces of the substrates to join the substrates together. Air is evacuated from between the substrates in order to obtain a vacuum assembly.
The sealant is typically made of a sealant glass, or frit. During manufacture of the PDP, the sealing process is performed by subjecting the substrates with the frit therebetween in an environment with a temperature that is higher than a temperature corresponding to a softening point of the frit to thereby seal the substrates. A predetermined pressure (e.g., 1˜2 kg/cm2) may be applied to an exterior of the substrates to realize more effective sealing. Such a pressure may be applied, for example, by a plurality of sealant clips that apply pressure to the substrates.
As an example of a technique for sealing a PDP, a sealing method for a PDP is disclosed in Korean Laid-Open Patent No. 2001-0004156. However, as disclosed in the patent, in the sealing process of flat panel displays, including PDPs, there is a high probability that minute leaks will occur at portions of the sealant area because of the joining characteristics of the frit and the upper and lower substrates.
Such a problem may be attributed to the state of deposition of the frit on the substrates. That is, the frit is generally deposited, with a uniform thickness, around the circumference of the substrates. No steps are taken to vary the thickness of the frit at specific areas, such as, the areas where the sealant clips are provided. As a result, the thickness of the frit varies in the regions where the sealant clips are mounted on the substrates.
In particular, the frit in the region where the sealant clips are provided becomes thinner than the frit where the sealant clips are not provided (a difference of approximately 20˜40 μm results). If minute gaps are formed, as a result of this difference in frit thickness in the regions where the substrates are sealed, noise is generated during operation of the PDP. This reduces the overall quality of the PDP.